This invention relates to thermosettable resin compositions having excellent physical and mechanical properties when cured.
Aromatic polycyanates which are thermosettable to polytriazines are known, for example, from U.S. Pat. Nos. 3,448,079; 3,694,410; 3,740,348; 3,755,402 and 4,094,852. Said polytriazines possess excellent heat resistance, however, their mechanical properties, especially tensile strength and elongation are deficient. Furthermore, there is substantial room for improvement in the moisture resistance of said polytriazines.
Polymaleimides which are thermosettable are known, for example, from U.S. Pat. No. 2,444,536 and from New Industrial Polymers, Rudolph D. Deanin (editor), ACS Symposium Series 4 published by American Chemical Society, Washington, D.C. (1972), pages 100-123. Said polymaleimides are typically difficult to process and cure due to high melting points, poor solvent solubility and slow curing rates. The thermoset (cured) polymaleimides are very brittle and thus of limited utility.
The present invention provides novel compositions which are thermosettable to useful polymeric (cured) compositions with improved mechanical strength both as laminates and clear, unfilled castings. Many of the compositions of the present invention possess improved heat resistance and improved moisture resistance when compared to the polytriazines of the prior art. In addition, many of the compositions of the present invention possess improved processability and high reactivity. These compositions are useful in the preparation of castings, laminates, coatings and the like.